Ultrafiltration devices have been used in the past for the separation of components of a fluid on the basis of the size, shape or physical character of the components through the use of hydraulic pressure. Using these techniques, one component of the fluid is selectively forced through a membrane to separate that component from the remainder of the mixture.
The selective membranes used in ultrafiltration techniques have conventionally been supported on a porous substrate. The fluid components passing through the selective membrane can then also continue to pass through the porous substrate for collection.
While a wide variety of membranes have been used for ultrafiltration separations, previously known membranes have frequently been found to have a limited service time before their rejection properties or filtrate fluxes became unsatisfactory. When the performance of the membrane became unsatisfactory, replacement of the porous support was often required because the membrane was not regenerable or replaceable in place to restore performance. Further, many known ultrafiltration membranes have little utility when used at elevated temperatures or with solvent or corrosive media such as fluids containing acetone or hydrochloric acid.